Good oil-repellent and water-repellent coatings may be provided to certain substrates by applying to a substrate fluorinated silanes in the molten state or dissolved in volatile organic solvents. The applied fluorinated silanes are cured by heating with a catalyst to chemically affix the fluorinated silanes to the substrates. (See, for example, U.S. Pat. No. 3,012,006 (Holbrook et al.)). However, the use of volatile organic solvents is generally harmful to the environment, and may be hazardous due to the flammability of the solvents. Therefore, an alternative means to apply fluorinated silanes to substrates was developed, which is to use aqueous delivery. (See, for examples, U.S. Pat. No. 5,274,159 (Pellerite et al.), U.S. Pat. No. 5,702,509 (Pellerite et al.), and U.S. Pat. No. 5,550,184 (Halling)).
One problem with known compositions for the aqueous delivery of fluorinated alkoxysilanes to substrates is that they may not have long shelf lives. Another problem is that they may require high-shear mixing before they are coated on a substrate. Known compositions have high solids content, which result in thick coatings.
In particular, U.S. Pat. No. 5,274,159 (Pellerite et al.) describes preparation of fluorinated alkoxysilanes that are self-emulsifying into water. Although they may be self-emulsifying providing good aqueous dispersions, the dispersions do not have relatively long shelf lives upon exposure to water, and they can be difficult to dilute due to their relatively high viscosities.
Although using aqueous delivery of fluorinated silanes, including self-emulsifying fluorinated alkoxysilanes, to substrates is known in the art, there continues to be a desire to provide compositions for aqueous delivery of self-emulsifying fluorinated alkoxysilanes that: 1) can be stored for relatively long periods of time; 2) do not require high-shear mixing or other input of mechanical energy; 3) have relatively low solids content, making them easier to coat thinly on glass and other substrates; and 4) at the same time, once applied to a substrate and cured, can provide durable coatings.